DUBLIN, Ohio — If you thought there ever was a doubt, you don’t know Phil Mickelson very well.

Mickelson announced on Saturday he will not play in the U.S. Open in two weeks so he can attend the high school graduation of his daughter Amanda.

“It’s one of those things that you just show up. You just need to be there,’’ Mickelson said after completing his third round of the Memorial at Muirfield Village.

Eighteen years ago at Pinehurst, Mickelson, with a beeper in his golf bag, was prepared to bolt from the 1999 U.S. Open with the birth of his first child imminent.

His wife, Amy, was instructed to beep him — even if it was in the middle of a round — when it was go time. She held off the birth with the help of some medication and Mickelson completed — and lost — that U.S. Open to Payne Stewart in a dramatic finish.

“Good luck with the baby,’’ Stewart told Mickelson in a moving moment of consolation during which he had both hands on the sides of Mickelson’s face. “There’s nothing greater than being a father.”

The next day, Amanda Mickelson was born.

On Thursday, June 15 — the same day as the opening round of the U.S. Open at Erin Hills in Wisconsin — Amanda will graduate from high school and her dad will be there.

Mickelson, who turns 47 on June 16, has finished runner-up in the Open a record six times. It remains the only major championship he has not won, the only piece missing to a rare and coveted career Grand Slam.

No matter. Mickelson always puts his family first. This is no exception. This was a no-brainer.

Payne Stewart consoles Phil Mickelson after his US Open victory in 1999.AP

So was flying home for a day right before the first round of the 2013 U.S. Open at Merion so he could attend Amanda’s eighth-grade graduation, at which she was speaking. Mickelson got back to Pennsylvania for the Open about four hours before his 7:11 a.m. first-round tee time and ended up nearly winning the tournament. It was, in fact, his sixth runner-up finish.

“Obviously, it’s a tournament that I want to win the most, and the only way to win is if you play and have a chance,’’ Mickelson said. “But this is one of those moments where you look back on life and you just don’t want to miss it. I’ll be really glad that I was there and present.’’

Amanda, the eldest of Mickelson’s three children, is going to be a freshman at Brown next fall. She is the high school president and, according to Mickelson, is giving the commencement speech.

The graduation is at 10 a.m. Pacific time, which would preclude Mickelson, even with use of his private jet, to make any first-round tee time work.

After a conversation with USGA executive director Mike Davis, Mickelson said there is no need to officially withdraw yet.

“You never know what might happen; maybe something comes up with the commencement, maybe something comes up with the weather,” he said. “I don’t know what will happen, but it doesn’t look very good. It would have to be something unforeseen. I’ll withdraw as close to the event as possible. But it doesn’t look good for me playing. But I’m really excited about this moment in our family’s life.’’

“Every year at the U.S. Open,” Mickelson said, “I think back about that ’99 Open.

“The birth of your child — any child, but especially your first child — is the most emotional event you can ever experience and share together with your wife. And I always think about that at the U.S. Open, I think about Payne Stewart and… I can’t believe how quickly time has gone by. Here [Amanda] is turning 18 and moving off to college, and I’m so proud of her. I’m excited to see what she has to say at her commencement.’’

Asked if he plans to help Amanda with her commencement speech, Mickelson said, “Probably not. No, actually, definitely not. She’s a better writer, more eloquent speaker, than I ever dreamed to be.’’